34 
Now, I would remind you that the chair will reconvene this meeting at 
precisely 10:50, at which time Dr. Singer will begin. We now adjourn for 
coffee. 
(Brief recess.) 
DR. FREDRICKSON: I would like to announce that some of the material 
that I advertised as being available has now been completely consumed. More 
copies are being made and will be available after lunch. 
We will resume now our session with a presentation by Dr. Maxine Singer, 
who is from the Laboratory of Biochemistry of the National Cancer Institute, 
a molecular biologist, but I believe not immediately working on recombinant 
DNA experiments herself at this present time. Dr. Singer will perform the 
difficult task of providing us with a summary and review of the proposed 
guidelines. 
Maxine? 
DR. SINGER: The guidelines that I am going to try to summarize for you 
this morning are the guidelines discussed and voted upon at the meeting of 
the advisory committee in La Jolla on December 4th and 5th. I am going to 
try to present a detailed view of the guidelines, but because of the time 
limitation, it will not be a comprehensive view. 
Dr. Berg has already defined the kinds of experiments to which the 
guidelines apply, and the first slide that I want to show you summarizes it 
again, and will serve to define a few of the terms as they are specifically 
used in the guidelines. 
Could I have the first slide, please? It is very similar to a slide 
that Dr. Berg showed you. 
At the upper left is a cell containing chromosomal DNA and several 
small, independent genetic elements. These small, independent DNA molecules 
can be isolated from the cell and can be manipulated to serve as one portion 
of the recombined DNA, the portion which is called the vector. 
Most such elements are circular DNA molecules, and they can be cleaved, 
as shown, by restriction endonucleases, to yield linear DNA strands that 
have either sticky ends or ends that can be made sticky. 
In most experiments the recombinant DNA will finally be reinserted into 
cells of the same species from which the vector was isolated, and it is the 
genetic information encoded in the DNA of the vector which ultimately is 
responsible for the continued existence and replication of the recombined 
DNA in the recipient cell. 
[175] 
